Solid state imaging device and electronic apparatus

ABSTRACT

Provided is a solid state imaging device including: a pixel portion where pixel sharing units are disposed in an array shape and where another one pixel transistor group excluding transfer transistors is shared by a plurality of photoelectric conversion portions; transfer wiring lines which are connected to the transfer gate electrodes of the transfer transistors of the pixel sharing unit and which are disposed to extend in a horizontal direction and to be in parallel in a vertical direction as seen from the top plane; and parallel wiring lines which are disposed to be adjacent to the necessary transfer wiring lines in the pixel sharing unit and which are disposed to be in parallel to the transfer wiring lines as seen from the top plane, wherein voltages which are used to suppress potential change of the transfer gate electrodes are supplied to the parallel wiring lines.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a solid state imaging device and an electronicapparatus adapted to a camera or the like employing the solid stateimaging device.

2. Description of the Related Art

As a solid state imaging device, there is known a CMOS solid stateimaging device. Since the CMOS solid state imaging device has a lowpower source voltage and low power consumption, the CMOS solid stateimaging device has been used for a digital still camera, a digital videocamera, and various types of mobile terminals such as a mobile phoneattached with a camera attached.

The CMOS solid state imaging device includes a pixel portion where aplurality of pixels including photodiodes as photoelectric conversionportions and a plurality of pixel transistors are disposed in atwo-dimensional array shape with regularity and a peripheral circuitportion which is disposed in the vicinity of the pixel portion.

In general, in a front illumination type CMOS solid state imaging devicein the related art, the interval between the wiring lines is configuredto be an interval defined by the minimum design rule so that the wiringlines provided to the pixel portion are not disposed to pass over thephotodiodes which are photoelectric conversion portions in the opticalpoint of view.

In the front illumination type CMOS solid state imaging device,generally, in the case where the accumulating time is long or in thecase where an amount of incident light is large, the accumulated chargesof the photodiode exceeds the capacitance of the photodiode so as tooverflow, so that a so-called blooming phenomenon occurs, which causesdeterioration of image quality. Therefore, in order to prevent theblooming, a so-called vertical overflow structure of releasing chargesto a substrate has been configured. In other words, in the situationwhere the transfer gate is turned off, the potential is designed to belowered, so that a decrease in a saturation signal amount Qs isprevented, and almost no influence is designed to be exerted to thepotential change of the preceding transfer gate, so that a variation inthe saturation signal amount is avoided.

In addition, recently, a back illumination type CMOS solid state imagingdevice has drawn attention (refer to Japanese Unexamined PatentApplication Publication Nos. 2007-115994 and 2003-31785). In the backillumination type CMOS solid state imaging device, light is incident toa rear surface of a substrate at a side opposing the side where wiringlines are disposed, and the wiring lines of a pixel portion may bedisposed to pass over photodiodes, so that a degree of freedom in thelayout is greatly increased. In involvement with miniaturization of apixel size, a pixel sharing type CMOS solid state imaging device whereone pixel transistor group excluding transfer transistors is shared by aplurality of photodiodes is also disclosed (refer to Japanese UnexaminedPatent Application Publication Nos. 2008-294218 and 2009-135319)

Until the pixel size is decreased down to about 1.5 μm, the layout maybe implemented by configured the interval between the wiring lines notso as to be narrowed by using the pixel sharing type. In addition, inthe back illumination type CMOS solid state imaging device, in general,the lateral overflow is formed as an approach for countering theblooming. In the lateral overflow, charges are allowed to be releasedthrough the floating diffusion portion from a portion under the transfergate. In the back illumination type CMOS solid state imaging device,there is a disadvantage in the potential change of the transfer gate dueto the influence of the lateral overflow structure. However, in the casewhere the pixel size is large, the interval between the transfer wiringlines may be configured to be relatively large, or the pixel sharingtype, where the maximum pixel aperture ratio may not be obtained but theinterval between the transfer wiring lines may be easily taken, has beenemployed to obtain relatively small coupling between the transfer wiringlines, so that the aforementioned problem has been avoided. In otherwords, if the pixel size is large, the interval between the wiring linesmay not be narrowed, so that no problem occurs in that signal loss dueto the potential change of the transfer gate according to the couplingbetween the transfer wiring lines. In addition, the pixel sharing typeis configured so vertical four pixels are shared without narrowing theinterval between the transfer wiring lines, so that no problem is causedby signal loss due to the potential change of the transfer gate.

SUMMARY OF THE INVENTION

For example, if the miniaturization of the pixel size proceeds down toabout 1 μm or less, in the back illumination type CMOS solid stateimaging device, although a degree of freedom in the layout of the wiringlines in the pixel portion is high, the interval between the adjacentwiring lines relatively reaches the interval defined by the design rule.In addition, in order to maximize the aperture ratio of the photodiodeby the miniaturization of the pixel size, if horizontal 2×vertical 2n(n=1, 2, . . . ) pixels are used as a pixel sharing unit, the wiringlines may have to be necessarily concentrated, so that the intervalbetween the adjacent wiring lines is decreased.

In this way, if the interval between the adjacent wiring lines is small,the capacitance coupling between the wiring lines may not be neglected.Particularly, in the transfer wiring line which supplies a pulse voltageto the transfer gate, if the voltage at the time of turning off thetransfer gate is changed due to the influence of other wiring lines, thepotential in the silicon under the transfer gate is changed. Due to thepotential change, the charges accumulated in the photodiodes are leakedinto a floating diffusion portion (FD), so that the saturation signalamount (Qs) may be changed, or so that a variation in the saturationsignal amount between photodiodes may be increased. Therefore, thesaturation signal amount is necessarily set to a low-levelspecification, so that there is a problem in terms of imagingcharacteristics.

Particularly, due to the aforementioned problem in terms of structure,the back illumination type CMOS solid state imaging device may have tobe configured as a lateral overflow type. In other words, the potentialof a portion under the transfer gate is intentionally configured to berelatively high even in the off state of the transfer gate in comparisonwith the front illumination type CMOS solid state imaging device, wherethe portion under some transfer gates may be necessarily opened so as tofacilitate the overflow. Therefore, due to the change in voltage of thetransfer gate, the potential change in the silicon is increased incomparison with the front illumination type CMOS solid state imagingdevice. As a result, problems occur in that the saturation signal amountis decreased or in that a variation in the saturation signal amount isincreased due to the influence of the capacitance coupling.

It is desirable to provide a solid state imaging device capable ofsuppressing a variation in a saturation signal amount involved withminiaturization of a pixel size.

It is desirable to provide an electronic apparatus such as a cameraemploying the solid state imaging device.

According to an embodiment of the invention, there is provided a solidstate imaging device including a pixel portion where pixel sharing unitsare aligned in an array shape and where another one pixel transistorgroup excluding transfer transistors is shared by a plurality ofphotoelectric conversion portions. The pixel portion is provided withtransfer wiring lines which are connected to the transfer gateelectrodes of the transfer transistors of the pixel sharing unit andwhich are disposed to extend in a horizontal direction and to be inparallel in a vertical direction as seen from the top plane. Inaddition, the pixel portion is provided with parallel wiring lines whichare disposed to be adjacent to the necessary transfer wiring lines inthe pixel sharing unit and which are disposed to be in parallel to thetransfer wiring lines as seen from the top plane. In addition, voltageswhich are used to suppress potential change of the transfer gateelectrodes are supplied to the parallel wiring lines. Preferably, as thevoltage, a pulse voltage or a constant voltage is used.

In the solid state imaging device according to the embodiment of theinvention, since the parallel wiring lines which supply the voltages forsuppressing the potential change of the transfer wiring lines aredisposed to be adjacent to the transfer wiring lines, the influence ofthe capacitance coupling between transfer wiring lines is decreased, sothat the potential change of the transfer gate electrode in the pixeldriving period is suppressed.

According to another embodiment of the invention, there is provided asolid state imaging device including a pixel portion where unit pixelsconfigured with a photoelectric conversion portion and a pixeltransistor are disposed in an array shape. The pixel portion is providedwith transfer wiring lines which are connected to the transfer gateelectrodes of transfer transistors included in the pixel transistors ofunit pixels and which are disposed to extend in a horizontal directionand to be in parallel in a vertical direction as seen from the topplane. In addition, the pixel portion is provided with parallel wiringlines which are disposed to be adjacent to the outermost transfer wiringlines and which are disposed to be in parallel to the transfer wiringlines as seen from the top plane, and a pulse voltage is supplied to atleast one of the parallel wiring lines.

In the solid state imaging device according to the embodiment of theinvention, the parallel wiring lines are disposed to be adjacent to theoutermost transfer wiring lines, and a pulse voltage is supplied to atleast one of the parallel wiring lines, so that the couplingcapacitances between the transfer wiring lines are equalized.Accordingly, the potential change of the transfer gate electrode in thepixel driving period is suppressed.

According to still another embodiment of the invention, there isprovided an electronic apparatus including: a solid state imagingdevice; an optical system which guides incident light to photodiodes ofthe solid state imaging device; and a signal processing circuit whichprocesses an output signal of the solid state imaging device. The solidstate imaging device is configured as the aforementioned solid stateimaging device according to the embodiment of the invention.Accordingly, the potential change of the transfer gate electrode in thepixel driving period is suppressed.

In an electronic apparatus according to the embodiment of the invention,since the aforementioned solid state imaging device according to theembodiment of the invention is included, the potential change of thetransfer gate electrode in the pixel driving period is suppressed.

According to a solid state imaging device according to the embodiment ofthe invention, since the potential change of the transfer gate electrodein the pixel driving period is suppressed, it is possible to suppressthe variation of the saturation signal amount involved with theminiaturization of the pixel size.

According to an electronic apparatus according to the embodiment of theinvention, since the potential change of the transfer gate electrode inthe pixel driving period is suppressed in the solid state imagingdevice, it is possible to suppress the variation of the saturationsignal amount involved with the miniaturization of the pixel size.Therefore, it is possible to provide a high-quality electronic apparatusof which the image quality is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of maincomponents of a solid state imaging device according to a firstembodiment of the invention.

FIG. 2 is a schematic diagram illustrating the more detailedconfiguration of the main components in the first embodiment of theinvention.

FIG. 3 is a schematic diagram illustrating a configuration of maincomponents of a solid state imaging device according to a secondembodiment of the invention.

FIG. 4 is a schematic diagram illustrating a configuration of maincomponents of a solid state imaging device according to a thirdembodiment of the invention.

FIG. 5 is a schematic diagram illustrating a configuration of maincomponents of a solid state imaging device according to a fourthembodiment of the invention.

FIG. 6 is a schematic diagram illustrating a configuration of maincomponents of a solid state imaging device according to a fifthembodiment of the invention.

FIG. 7 is a schematic diagram illustrating a configuration of maincomponents of a solid state imaging device according to a sixthembodiment of the invention.

FIG. 8 is a schematic diagram illustrating an example of a CMOS solidstate imaging device adapted to a solid state imaging device accordingto the embodiment of the invention.

FIG. 9 is an equivalent circuit diagram illustrating an example of aunit pixel.

FIG. 10 is an equivalent circuit diagram illustrating another example ofa unit pixel.

FIG. 11 is an equivalent circuit diagram illustrating an example of apixel sharing unit.

FIG. 12 is a schematic diagram illustrating a configuration of maincomponents of an electronic apparatus according to a seventh embodimentof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the inventions (hereinafter, referred to asembodiments) will be described. The description will be made in thefollowing order.

1. Example of Schematic Configuration of CMOS Solid State Imaging device

2. First Embodiment (Example of Configuration of Solid State Imagingdevice)

3. Second Embodiment (Example of Configuration of Solid State Imagingdevice)

4. Third Embodiment (Example of Configuration of Solid State Imagingdevice)

5. Fourth Embodiment (Example of Configuration of Solid State Imagingdevice)

6. Fifth Embodiment (Example of Configuration of Solid State Imagingdevice)

7. Sixth Embodiment (Example of Configuration of Solid State Imagingdevice)

8. Seventh Embodiment (Example of Electronic Apparatus)

1. Example of Schematic Configuration of CMOS Solid State Imaging Device

FIG. 8 illustrates a schematic configuration of an example of a CMOSsolid state imaging device adapted to the embodiments of the invention.In this example, as illustrated in FIG. 8, the solid state imagingdevice 1 includes a pixel portion 3 (a so-called imaging area), where aplurality of pixels 2 including photoelectric conversion portions aredisposed regularly in a two-dimensional array on a semiconductorsubstrate 11, for example, a silicon substrate, and a peripheral circuitportion. As the pixel 2, a unit pixel constructed with one photoelectricconversion portion and a plurality of pixel transistors may be employed.In addition, as the pixel 2, a so-called pixel sharing structure, whereone group of pixel transistors excluding transfer transistors isconfigured to be shared by a plurality of the photoelectric conversionportions, may be employed. As described later, the plurality of pixeltransistors may be constructed with three transistors including atransfer transistor, a reset transistor, and an amplification transistoror four transistors including a selection transistor and theaforementioned three transistors.

The peripheral circuit portion includes a vertical driving circuit 4,column signal processing circuits 5, a horizontal driving circuit 6, anoutput circuit 7, a control circuit 8, and the like.

The control circuit 8 receives an input clock and data commanding anoperation mode or the like and outputs data such as internal informationon the solid state imaging device. In other words, the control circuit 8generates a clock signal or a control signal used as a reference foroperations of the vertical driving circuit 4, the column signalprocessing circuits 5, the horizontal driving circuit 6, and the likeaccording to a vertical synchronization signal, a horizontalsynchronization signal, and a master clock. Next, the control circuit 8inputs these signals to the vertical driving circuit 4, the columnsignal processing circuits 5, the horizontal driving circuit 6, and thelike.

The vertical driving circuit 4 is configured with, for example, shiftregisters. The vertical driving circuit 4 selects a pixel driving wiringline and supplies a pulse for driving pixels to the selected pixeldriving wiring line, so that the pixels are driven in units of a row. Inother words, the vertical driving circuit 4 selectively drives thepixels 2 of the pixel portion 3 in units of a row sequentially in thevertical direction. Next, pixel signals corresponding to signal chargesgenerated according to received light amounts in the photoelectricconversion devices, for example, photodiodes of the pixels 2 aresupplied through the vertical signal lines 9 to the column signalprocessing circuits 5.

The column signal processing circuit 5 is disposed corresponding to, forexample, each column of the pixels 2 to perform a signal process such asa process of removing noise from a signal output from one row of pixels2 for each column of the pixels. In other words, the column signalprocessing circuit 5 performs a signal process such as CDS for removingfixed pattern noise unique to the pixel 2, signal amplification, and ADconversion. Horizontal selection switches (not shown) are providedbetween the output stages of the column signal processing circuits 5 anda horizontal signal line 10.

The horizontal driving circuit 6 is configured with, for example, shiftregisters. The horizontal driving circuit 6 sequentially outputshorizontal scan pulses to sequentially select the column signalprocessing circuits 5, so that the pixel signals are allowed to beoutput from the column signal processing circuits 5 to the horizontalsignal line 10.

The output circuit 7 performs a signal process on the signals, which aresequentially output from the column signal processing circuits 5 throughthe horizontal signal line 10, and outputs processed signals. Forexample, in some cases, the output circuit 7 may perform only abuffering process, and in other cases, the output circuit 7 may alsoperform various digital signal processes such as a black level adjustingprocess and a column variation correction process. An input/outputterminal 12 communicates signals with external portions.

FIG. 9 illustrates an equivalent circuit of an example of a unit pixel.The unit pixel 21 according to the example, which is surrounded by adashed line, is configured with a photodiode PD which is a photoelectricconversion portion and three pixel transistors. The three pixeltransistors include a transfer transistor Tr1, a reset transistor Tr2,and an amplification transistor Tr3. Herein, as the pixel transistorsTr1 to Tr3, for example, n-channel MOS transistors are used.

The photodiode PD is connected to the transfer transistor Tr1. Thetransfer transistor Tr1 is connected through a floating diffusionportion FD to the reset transistor Tr2. The signal charges (in thiscase, electrons), which are photoelectrically converted by thephotodiode PD and accumulated therein, are transferred to the floatingdiffusion portion FD by applying a transfer pulse φTRG to the gate ofthe transfer transistor Tr1 through the transfer wiring line 14.

The floating diffusion portion FD is connected to the gate of theamplification transistor Tr3. In this case, the source of the resettransistor Tr2 (the drain of the transfer transistor Tr1) is configuredas the floating diffusion portion FD. Before transferring the signalcharges from the photodiode PD to the floating diffusion portion FD, byapplying a reset pulse φRST to the reset gate through the reset wiringline 15, the potential of the floating diffusion portion FD is reset.

The source of the amplification transistor Tr3 is connected to thevertical signal line 9. The selection and non-selection of a pixel isdistinguished by using the potential of the floating diffusion portionFD. The amplification transistor Tr3 outputs the potential of thefloating diffusion portion FD, after the resetting is performed by thereset transistor Tr2, as the reset level to the vertical signal line 9.In addition, the amplification transistor Tr3 outputs the potential ofthe floating diffusion portion FD, after the transferring of the signalcharges is performed by the transfer transistor Tr1, as the signal levelto the vertical signal line 9.

FIG. 10 illustrates an equivalent circuit of another example of the unitpixel. The unit pixel 22 according to the example is configured with aphotodiode PD which becomes a photoelectric conversion portion and fourpixel transistors. The four pixel transistors include a transfertransistor Tr1, a reset transistor Tr2, an amplification transistor Tr3,and a selection transistor Tr4. In this example, as these pixeltransistors Tr1 to Tr4, for example, n-channel MOS transistors may beused.

The photodiode PD is connected to the transfer transistor Tr1. Thetransfer transistor Tr1 is connected to through the floating diffusionportion FD to the reset transistor Tr2. The signal charges (in thiscase, electrons), which are photoelectrically converted by thephotodiode PD and accumulated therein, are transferred to the floatingdiffusion portion FD by applying a transfer pulse φTRG to the gate ofthe transfer transistor Tr1 through the transfer wiring line 14.

The floating diffusion portion FD is connected to the gate of theamplification transistor Tr3. Before transferring the signal chargesfrom the photodiode PD to the floating diffusion portion FD, by applyinga reset pulse φRST to the reset gate through the reset wiring line 15,the potential of the floating diffusion portion FD is reset.

The source of the amplification transistor Tr3 is connected to the drainof the selection transistor Tr4, and the source of the selectiontransistor is connected to the vertical signal line 9. By applying aselection pulse φSEL to the gate of the selection transistor Tr4 throughthe selection wiring line 16, the on state is obtained, so that a pixelis selected. The amplification transistor Tr3 outputs the potential ofthe floating diffusion portion FD, after the resetting is performed bythe reset transistor Tr2, as the reset level through the selectiontransistor Tr4 to the vertical signal line 9. In addition, theamplification transistor Tr3 outputs the potential of the floatingdiffusion portion FD, after the transferring of the signal charges isperformed by the transfer transistor Tr1, as the signal level throughthe selection transistor Tr4 to the vertical signal line 9. In addition,a configuration where the selection transistor 115 is connected to thedrain of the amplification transistor Tr3 may be employed. In this case,the source of the amplification transistor Tr3 is connected to thevertical signal line 9.

FIG. 11 illustrates an equivalent circuit of a multi-pixel sharingstructure. In FIG. 11, a 2-pixel sharing unit 23, a 4-pixel sharing unit24, and an 8-pixel sharing unit 25 are illustrated. For example, the2-pixel sharing unit 23 is configured by allowing two photodiodes PD1and PD2, which become photoelectric conversion portions, to shareanother one pixel transistor group excluding the transfer transistorsTr11 and Tr12. In other words, the 2-pixel sharing unit 23 is configuredwith two photodiodes PD, two transfer transistors Tr11 and Tr12, afloating diffusion portion FD, a reset transistor Tr2, an amplificationtransistor Tr3, and a selection transistor Tr4. In addition, aconfiguration where the selection transistor is omitted may be employed.The photodiodes PD1 and PD2 are connected to the corresponding transfertransistors Tr11 and Tr12. The transfer transistors Tr11 and Tr12 areconnected through the shared floating diffusion portion FD to the resettransistor Tr2, and the floating diffusion portion FD is connected tothe gate of the amplification transistor Tr3. The source of theamplification transistor Tr3 is connected to the drain of the selectiontransistor Tr4. The source of the selection transistor Tr4 is connectedto the vertical signal line 9. The transfer pulses φTG1 and φTG2 areapplied to the gates of the transfer transistors Tr11 and Tr12 throughthe transfer wiring lines 31 and 32. The reset pulse φRST is applied tothe gate of the reset transistor Tr2 through the reset wiring line 15.The selection pulse φSEL is applied to the gate of the selectiontransistor Tr4 through the selection wiring line 16.

The 4-pixel sharing unit 24 is configured by adding two photodiodes PD3and PD4 and two transfer transistors Tr13 and Tr14 to the circuitconfiguration of the 2-pixel sharing unit 23. In other words, thecorresponding four transfer transistors Tr11 to Tr14 are connected to atotal of four photodiodes PD [PD1 to PD4], and the sources of thetransfer transistors Tr11 to Tr14 are commonly connected to the floatingdiffusion portion FD.

The 8-pixel sharing unit 25 is configured by adding four photodiodes PD5to PD8 and four transfer transistors Tr15 to Tr18 to the circuitconfiguration of the 4-pixel sharing unit 24. In other words, thecorresponding eight transfer transistors Tr11 to Tr18 are connected to atotal of eight photodiodes PD [PD1 to PD8], and the sources of thetransfer transistors Tr11 to Tr18 are commonly connected to the floatingdiffusion portion FD.

In any one of the cases of FIGS. 9, 10, and 11, although voltages aresupplied to the drain terminals t1 and t2 of the reset transistor andthe amplification transistor, any voltage supply method such as acommon/non-common voltage supply, constant (fixed) voltage supply,voltage supply using pulse driving, or the like may be employed. Ingeneral, the power source VDD is supplied to the drain terminals t1 andt2. A two-series power source may be used. In other words, the drainterminals of the reset transistor and the amplification transistor maybe commonly connected or may be non-commonly (independently) configured.In the case where the drain terminals are independently configured,different power source voltages may be set thereto. In addition, sinceall the aforementioned drain terminals are assumed to be supplied withthe power source voltage, the constant (fixed) voltage is generallyemployed. However, pulse driving, that is, supplying a high voltage atonly the driving period may be employed without causing a problem.

Now, a basic concept of the invention is described. In a CMOS solidstate imaging device, although the suppression of the potential changein the silicon caused by the potential change of the transfer gate isconsidered in order to avoid a decrease in the saturation signal amount,it is very difficult to implement the suppression. In other words, sincelarge capacitance couplings between the wiring lines actually exist, itis difficult to suppress the potential change. In addition, in the backillumination type CMOS solid state imaging device, lateral overflow isnecessarily formed to overcome the deterioration in the image quality,and it is actually difficult to sustain a relatively low potential atthe off time of the transfer gate in comparison with a frontillumination type CMOS solid state imaging device.

If the potential change of the transfer gate is equalized in order tosuppress the variation in the saturation signal amount, the potentialchange in the silicon under the transfer gate is also equalized, so thatthe variation in the saturation signal amount is removed. In order toequalize the potential changes of the transfer gates, reformation of thelayout of the wiring lines in the pixel portion may have to beperformed. Therefore, if the coupling capacitance between the transferwiring line and the other transfer wiring line is uniformed by designingthe layout of the wiring lines in the pixel portion, the potentialchanges of the transfer wiring lines are equalized among the transfergates, the variation in the saturation signal amount may be suppressed.The invention is to provide a CMOS solid state imaging device capable ofsuppressing the variation in the saturation signal amount based on thisconcept.

The invention may be adapted to all the solid state imaging device wherethe pixels having the aforementioned configuration are disposed in atwo-dimensional array shape. Particularly, the embodiment may be veryappropriately adapted to a pixel sharing CMOS solid state imagingdevice. In addition, the embodiment may be very appropriately adapted toa back illumination type CMOS solid state imaging device.

2. First Embodiment Example of Configuration of Solid State ImagingDevice

FIG. 1 illustrates a solid state imaging device according to a firstembodiment of the invention. The embodiment may be adapted to a backillumination type CMOS solid state imaging device, where pixel sharingunits of four pixels, eight pixels, or horizontal 2×vertical 2n (n is apositive integer, that is, n=1, 2, 3, . . . ) pixels are aligned in atwo-dimensional array shape. As the pixel sharing unit, horizontal2×vertical 2 (total four) pixels constitute one unit irrespective of thenumber of shared pixels. Therefore, in FIG. 1, the embodiment isdescribed by using one unit of the horizontal 2×vertical 2 (total four)pixels.

As the solid state imaging device according to the first embodiment, aback illumination type CMOS solid state imaging device where 8-pixelsharing units are disposed in a two-dimensional array shape is adapted.In the solid state imaging device 41 according to the first embodiment,as illustrated in FIG. 1, a pixel portion is configured by disposing8-pixel sharing units 42, where photodiodes PD [PD1 to PD8] of eightpixels are disposed, in a two-dimensional array shape. Similarly to ageneral case, in the back illumination type CMOS solid state imagingdevice 41, pixel transistors are formed on the front surface of asemiconductor substrate, and a wiring line layer where a plurality oflayers of wiring lines constructed with metal layers are disposed isformed over the pixel transistors with an interlayer insulating layerinterposed therebetween. A color filter layer and on-chip lenses areformed on the rear surface of the semiconductor substrate, and light isincident from the rear surface side of the substrate. In other words,the back illumination type has a configuration where the wiring linelayer is formed on the side opposite to the light incident plane.

In the 8-pixel sharing unit 42, two sets of configurations where onefloating diffusion portion FD is shared by horizontal 2×vertical 2(total four) photodiodes PD are disposed vertically. In other words, thefirst configuration portion 43 and the second configuration portion 44are disposed in the vertical direction by using horizontal 2×vertical 2(total four) pixels as one unit.

The upper-side first configuration portion 43 is configured to have fourphotodiodes PD1 to PD4, four transfer gate electrodes 461 to 464corresponding to the four photodiodes PD1 to PD4, and a first floatingdiffusion portion FD1. Each of the transfer transistors Tr11 to Tr14 isconfigured with each of the photodiodes PD1 to PD4, the first floatingdiffusion portion FD1, and each of the transfer gate electrodes 461 to464. The floating diffusion portion FD1 is disposed at the centralportion surrounded by the four photodiodes PD1 to PD4, and each of thetransfer gate electrodes 461 to 464 is disposed at the positioncorresponding to the corner portion of each of the photodiodes PD1 toPD4.

The lower-side second configuration portion 44 is configured to havefour photodiodes PD5 to PD8, four transfer gate electrodes 465 to 468corresponding to the four photodiodes PD5 to PD8, and a second floatingdiffusion portion FD2. Each of the transfer transistors Tr15 to Tr18 isconfigured with each of the photodiodes PD5 to PD8, the second floatingdiffusion portion FD2, and each of the transfer gate electrodes 465 to468. The floating diffusion portion FD2 is disposed at the centralportion surrounded by the four photodiodes PD5 to PD8, and each of thetransfer gate electrodes 465 to 468 is disposed at the positioncorresponding to the corner portion of each of the photodiodes PD5 toPD8.

A selection transistor Tr4 and an amplification transistor Tr3 aredisposed between the first configuration portion 43 and the secondconfiguration portion 44. A reset transistor Tr2 is disposed under thelower-side second configuration portion 44. The selection transistor Tr4includes a pair of source/drain regions 47 and 48 and a selection gateelectrode 51. The amplification transistor Tr3 includes a pair ofsource/drain regions 48 and 49 and an amplification gate electrode 52.The reset transistor Tr2 includes a pair of source/drain regions 53 and54 and a reset gate electrode 55. The aforementioned gate electrodes areconstructed with, for example, a polysilicon layer. The first floatingdiffusion portion FD1 and the second floating diffusion portion FD2 areconnected to the amplification gate electrode 52 of the amplificationtransistor Tr3 and the source region of the reset transistor Tr2.

As characteristic configurations of the embodiment, the lower-sidesecond configuration portion 44 surrounded by the dashed line of FIG. 1and the (horizontal 2×vertical 2) pixels having a reset transistor Tr2,an amplification transistor Tr3, and a selection transistor Tr4 aredescribed. The upper-side first configuration portion 43 also hassubstantially the same configuration.

As seen from the top plane, the transfer wiring lines 35 to 38, whichare electrically connected to the transfer gate electrodes 465 to 468,are disposed to extend in the horizontal direction of the pixel portionand to be in parallel to each other in the vertical direction with anecessary interval. For example, at least one transfer wiring line amongthe four transfer wiring lines 35 to 38 is disposed to be in parallel soas to traverse the substantially central portions of the photodiodes PD.In this example, the transfer wiring lines 35 and 38 are configured soas to traverse the substantially central portions of the photodiodes PD.In this case, the four transfer wiring lines 35 to 38 preferably havethe same line width and the same interval between the wiring lines, butthese wiring lines may not necessarily have the same line width and thesame interval. As seen from the top plane, the four transfer wiringlines 35 to 38 may have to be disposed to be in parallel by using ametal layer in the later-described same layer or using metal layers ofdifferent layers.

At the outer side of the outermost transfer wiring lines 35 and 38,there are later-described parallel wiring lines which are adjacent tothe outermost transfer wiring lines 35 and 38 and which are in parallelto the transfer wiring lines 35 and 38 as seen from the top plane, andat least one of the parallel wiring lines is applied with a pulsevoltage. In this example, with respect to the outermost transfer wiringlines 35 and 38, the two parallel wiring lines 57 and 59 and the twoparallel wiring lines 58 and 60 are disposed respectively. For example,in the case where reading is performed sequentially from the lower-sidetransfer wiring line 38 toward the upper-side transfer wiring line 35, apulse voltage is applied to at least the one parallel wiring line, thatis, one of the parallel wiring lines 58 and 60 corresponding to thelower-side outermost transfer wiring line 38. On the contrary, in thecase where reading is performed sequentially from the upper-sidetransfer wiring line 35 toward the lower-side transfer wiring line 38, apulse voltage is applied to at least the one parallel wiring line, thatis, one of the parallel wiring lines 57 and 58 corresponding to theupper-side outermost transfer wiring line 35. A sufficient effect may beobtained only by supplying a pulse voltage to one parallel wiring linecorresponding to one of the outermost transfer wiring lines. On thecontrary, in the configuration where one parallel wiring linecorresponding to each of the outermost transfer wiring lines is suppliedwith a pulse voltage, that is, in the configuration where two parallelwiring lines are simultaneously supplied with pulse voltages, since thechange is increased, the configuration is not preferable. For example,since the transfer wiring line 37 is influenced by only the transferwiring line 38, it is preferable that the transfer wiring line 38 isalso influenced to the same extent. The parallel wiring lines may beconstructed with a metal layer in the same layer as the transfer wiringlines 35 to 38 or as the metal layers in the upper and lower adjacentlayers.

In this example, parallel wiring lines 57 to 60 are aligned at outersides of the outermost transfer wiring lines 35 and 38 so as to beparallel to the transfer wiring lines 35 and 38 as seen from the topplane. In other words, the parallel wiring lines 57 and 59 are alignedat the outer side of the transfer wiring line 35, and the parallelwiring lines 58 and 60 are aligned at the outer side of the transferwiring line 38.

The parallel wiring line 57 is aligned along the amplificationtransistor Tr3 and the selection transistor Tr4. The parallel wiringline 59 is disposed between the parallel wiring line 57 and the transferwiring line 35. The parallel wiring line 58 is aligned along the resettransistor Tr2. The parallel wiring line 60 is disposed between theparallel wiring line 58 and the transfer wiring line 38.

For example, the transfer wiring lines 35 to 38 and the parallel wiringlines 57 and 58 are constructed with a metal layer in the same layer,and the parallel wiring lines 59 and 60 are constructed with metallayers in a layer upwardly or downwardly adjacent to the metal layers ofthe transfer wiring lines 35 to 38 and the parallel wiring lines 57 and58.

In addition, the four transfer wiring lines 35 to 38 may be formed to bedivided into two layers, that is, upper and lower adjacent metal layersand to be in parallel to each other. In this case, as seen from the topplane, the four transfer wiring lines are disposed in parallel to eachother.

In addition, as another example, the four transfer wiring lines 35 to 38may be formed to be divided into two layers, that is, the upper andlower adjacent metal layers and to be in parallel to each other so thatthe upper and lower transfer wiring lines are overlapped with eachother. In the recent process, interlayer thickness may be reduced so asto be close to the interval between wiring lines in the same layer, andthe intervals between the transfer wiring lines 35 to 38 may beuniformed. Therefore, in this case, it is possible to equalize thecoupling capacitances between the four transfer wiring lines 35 to 38.

A constant voltage or a pulse voltage is applied to each of the parallelwiring lines 57, 58, 59, and 60. As the constant voltage, for example, apower source voltage or a ground voltage may be used. As the pulsevoltage, a pulse voltage other than the transfer pulse, for example, areset pulse or a selection pulse may be used.

For example, in the case of the parallel wiring lines 57 and 59, a pulsevoltage is applied to the parallel wiring line 57, and a constantvoltage is applied to the parallel wiring line 59. On the contrary, aconstant voltage is applied to the parallel wiring line 57, and a pulsevoltage is applied to the parallel wiring line 59. In the case of theparallel wiring lines 58 and 60, a pulse voltage is applied to theparallel wiring line 58, and a constant voltage is applied to theparallel wiring line 60. On the contrary, a constant voltage is appliedto the parallel wiring line 58, and a pulse voltage is applied to theparallel wiring line 60.

As a detailed example, the reset pulse voltage and the selection pulsevoltage may be set to pulse voltages, and the power source voltage maybe set to a constant voltage. In other words, the upper-side parallelwiring line 59 may be set to the selection wiring line connected to theselection gate electrode 51; the parallel wiring line 57 at the outerside thereof may be set to the power source wiring line, the lower-sideparallel wiring line 60 may be set to the reset wiring line connected tothe reset gate electrode 55; and the parallel wiring line 58 at theouter side thereof may be set to the power source wiring line.Otherwise, on the contrary, the upper-side parallel wiring line 59 maybe set to the power source wiring line; the parallel wiring line 57 atthe outer side thereof may be set to the selection wiring line; and thelower-side parallel wiring line 60 may be set to the power source wiringline; and the parallel wiring line 58 at the outer side thereof may beset to the reset wiring line. In the example of FIG. 1, since thetwo-series power source is used, the constant voltages supplied to theparallel wiring lines 57 and 58 or the parallel wiring lines 59 and 60at the two outer sides of the transfer wiring lines 35 to 38 become thepower source voltages.

In the embodiment, it is preferable that the layout is performed so thatthe coupling capacitances between the transfer wiring lines 35 to 38 andthe wiring lines adjacent thereto are equal to each other and so thatthe intervals between the transfer wiring lines 35 to 38 and theparallel wiring lines 59 and 60 or 57 and 58 of the outer side thereof,which supply pulse voltages, are substantially equal to each other. Forexample, in any one of the case where pulse voltages are supplied to theparallel wiring lines 59 and 60 and the case where pulse voltages aresupplied to the parallel wiring lines 59 and 58, it is preferable thatthe intervals between the adjacent wiring lines are configured so as tobe substantially equal to each other.

The first embodiment is described in detail with reference to FIG. 2.FIG. 2 illustrates a configuration where two sets of 8-pixel sharingunits 42 are aligned in the vertical direction. In the illustratedexample, the parallel wiring line 59 is set to a selection wiring linefor supplying the selection pulse φSEL; the parallel wiring line 60 isset to a reset wiring line for supplying the reset pulse φRST; and theparallel wiring lines 57 and 58 are set to power source wiring lines forsupplying the power source voltage. Hereinafter, the parallel wiringlines are referred to as the selection wiring line 59, the reset wiringline 60, the power source wiring lines 59 and 58.

In this example, in the 8-pixel sharing unit 42, the selection wiringlines 59 are disposed to be in parallel to each other in the two sidesof the parallel wiring line 57 with the parallel wiring line 57, whichis the power source wiring line, interposed therebetween. The twoselection wiring lines 59 are electrically connected to each other. Inaddition, at the outer side of the lower-side power source wiring line58, a photodiode PD and a ground wiring line 61 for supplying astabilized well contact voltage, that is, a ground voltage to asemiconductor well area, where the pixel transistor is formed, aredisposed. In FIG. 2, the transfer wiring lines 31 to 38 are electricallyconnected to the transfer gate electrodes 461 to 468 (refer to thereference numerals in FIG. 1) of the corresponding transfer transistorsTr11 to Tr18 (refer to the reference numerals in FIG. 1).

In the aforementioned solid state imaging device according to the firstembodiment, the transfer wiring lines 35 to 38 are disposed in parallel,and the parallel wiring lines 57 and 59 and the parallel wiring lines 58and 60 are disposed to be adjacent to the outermost transfer wiringlines 35 and 38. In addition, in the case where the parallel wiringlines 59 and 60 or the parallel wiring lines 57 and 58 are set to thepulse wiring lines, all the transfer wiring lines 35 to 38 including theoutermost transfer wiring lines 35 and 38 exist in an extremely closerange from the pulse wiring lines. Therefore, the potential changes ofall the transfer wiring lines 35 to 38 in the pixel driving period areequalized by the capacitance coupling, so that it is possible tosuppress the variation in the saturation signal amount between thepixels. In other words, although the miniaturization of the pixel sizeproceeds, it is possible to suppress the potential change of thetransfer gate electrode, and it is possible to suppress the potentialchange in the silicon under the transfer gate, so that it is possible tosuppress the variation in the saturation signal amount between thepixels. For this reason, the specification of the saturation signalamount may be set to be high, so that it is possible to improve pixelcharacteristics (saturation signal amount).

Since the wiring line interval that is arbitrary defined may be changedwithin design rule, the fine adjustment may be performed by changing thewiring line interval.

Even in the case where any one of parallel wiring lines 57 or 59 or anyone of parallel wiring lines 58 or 60 among the parallel wiring lines isset to a pulse voltage supply wiring line, the coupling capacitancesbetween the adjacent wiring lines in the transfer wiring lines 35 to 38are uniformed, it is possible to suppress the potential change of thetransfer gate electrodes. Therefore, although the miniaturization of thepixel size is proceeding, it is possible to suppress the potentialchange in the silicon under the transfer gate, so that it is possible tosuppress the variation in the saturation signal amount between thepixels.

The effect according to the configuration where at least one of theparallel wiring lines is used as a pulse voltage supply line isdescribed. The four parallel-disposed transfer wiring lines 35 to 38 areinfluenced by one adjacent transfer wiring line except for the outermosttransfer wiring line. Therefore, since the outermost transfer wiringline is also influenced by the one adjacent parallel wiring linesupplied with a pulse voltage, it is preferable that the outermosttransfer wiring line is influenced similarly to the other transferwiring lines. Since potential change may be controlled by the intervalbetween the wiring lines, even in the case where the two parallel wiringlines adjacent to the two outermost transfer wiring lines are used asthe wiring lines which supply pulse voltages, it may equalize thepotential change. However, if both wiring lines are in the constantvoltages, the potential change does not occur. For example, since thetransfer wiring lines 35 to 37 and the transfer wiring line 38 aredifferent from each other in the potential change, a variation in asaturation signal amount occurs.

On the other hand, since there is a parallel wiring line supplying aconstant voltage, it is possible to easily equalize the amount of thepotential change of the outermost wiring line. If one of the twoparallel wiring lines is the pulse wiring line, the outermost transferwiring line 38 is influenced by one pulse wiring line, and theintermediate transfer wiring lines, for example, transfer wiring lines35 to 37 can also be easily influenced to the same extent. However, ifthe two parallel wiring lines are the pulse wiring lines, one parallelwiring line may have to be separated by a considerable interval. If not,the potential change of the outermost transfer wiring line is increased,so that the suppression of the variation of the saturation signal amountmay not be easily obtained.

As seen from the top plane, at least one transfer wiring line (in thisexample, the transfer wiring lines 35 and 38) is disposed in thehorizontal direction to pass over the photodiode PD, preferably, totraverse the substantially central portions of the photodiodes PD, sothat the interval between the transfer wiring lines 35 and 38 may beincreased. The influence of the capacitance coupling between the wiringlines is decreased as much as the interval between the transfer wiringlines is increased, and the potential change at the portion under thegate at the charge accumulating period is suppressed, so that it ispossible to suppress the variation of the saturation signal amount. Inparticular, the embodiment may be very appropriately adapted to a backillumination type CMOS solid state imaging device.

3. Second Embodiment Example of Configuration of Solid State ImagingDevice

FIG. 3 illustrates a solid state imaging device according to a secondembodiment of the invention. The embodiment may be adapted to a backillumination type CMOS solid state imaging device, where pixel sharingunits of 4 pixels, 8 pixels or horizontal 2×vertical 2n (n is a positiveinteger, that is, n=1, 2, 3, . . . ) pixels are aligned in atwo-dimensional array shape. As the pixel sharing unit, horizontal2×vertical 2 (total four) pixels constitute one unit irrespective of thenumber of shared pixels. Therefore, similarly to FIG. 1, in FIG. 3, theembodiment is described by using one unit of the horizontal 2×vertical 2(total four) pixels.

As the solid state imaging device according to the second embodiment, aback illumination type CMOS solid state imaging device where 8-pixelsharing units are disposed in a two-dimensional array shape is adapted.The solid state imaging device 71 according to the second embodiment isconfigured by further inserting shield wiring lines 63 between thewiring lines of the transfer wiring lines 35 to 38 and between theoutermost transfer wiring lines 35 and 38 and the parallel wiring lines59 and 60 adjacent thereto in the solid state imaging device 41according to the first embodiment of FIG. 1. The shield wiring line 63is preferably fixed to a power source voltage or a ground voltage.However, the shield wiring line 63 may be floated in terms of apotential. The shield wiring line 63 is preferably constructed with ametal layer in the same layer as the transfer wiring lines 35 to 38. Inaddition, the shield wiring line 63 may be constructed with a metallayer upwardly or downwardly adjacent to the metal layer which becomes atransfer wiring line. The shield wiring line 63 is a wiring line foravoiding direct capacitance coupling between the transfer wiring lines35 to 38 or between the outermost transfer wiring lines 35 and 38 andthe parallel wiring lines adjacent thereto, for example, the parallelwiring lines 59 and 60.

The other configurations are the same as those of the first embodimentwhich is described with reference to FIGS. 1 and 2. Therefore, the samecomponents corresponding to those of FIG. 1 are denoted by the samereference numerals, and the redundant description thereof is omitted.

In the solid state imaging device 71 according to the second embodiment,the shield wiring lines 63 are inserted between the wiring lines of thetransfer wiring lines 35 to 38 and between the outermost transfer wiringlines 35 and 38 and the parallel wiring lines 59 and 60 adjacentthereto, so that direct capacitance coupling between the transfer wiringlines is avoided. Accordingly, the potential changes of all the transferwiring lines 35 to 38 in the pixel driving period is suppressed, so thatit is possible to suppress the variation in the saturation signal amountbetween the pixels. The solid state imaging device 71 is combined withthe effect described with reference to FIG. 1, which is obtained by thelayout of the pulse wiring lines according to the parallel wiring linesadjacent to the outermost transfer wiring lines 35 and 38, so that avariation in a saturation signal amount is further suppressed.Therefore, although the miniaturization of the pixel size is proceeding,it is possible to suppress the potential change in the silicon under thetransfer gate, so that it is possible to suppress the variation in thesaturation signal amount between the pixels. For this reason, thespecification of the saturation signal amount may be set to be high, sothat it is possible to improve pixel characteristics.

However, in the case where the shield wiring line is hard to insert interms of the design rule or in the case where too excessive insertion ofthe shield wiring line with a minimum width has no effect in terms ofproduction yields, the shield wiring line is not inserted.

4. Third Embodiment Example of Configuration of Solid State ImagingDevice

FIG. 4 illustrates a solid state imaging device according to a thirdembodiment of the invention. The embodiment may be adapted to a backillumination type CMOS solid state imaging device, where pixel sharingunits of 4 pixels, 8 pixels, or horizontal 2×vertical 2n (n is apositive integer, that is, n=1, 2, 3, . . . ) pixels are aligned in atwo-dimensional array shape. As the pixel sharing unit, horizontal2×vertical 2 (total four) pixels constitute one unit irrespective of thenumber of shared pixels. Therefore, similarly to FIG. 1, in FIG. 4, theembodiment is described by using one unit of the horizontal 2×vertical 2(total four) pixels.

As the solid state imaging device 73 according to the third embodiment,a back illumination type CMOS solid state imaging device where 8-pixelsharing units are disposed in a two-dimensional array shape is adapted.In the solid state imaging device 73 according to the third embodiment,four transfer wiring lines 35 to 38 and parallel wiring lines 57 and 58,which are adjacent to the outermost transfer wiring lines 35 and 38 andare supplied with pulse voltages, are configured to be constructed witha metal layer in the same layer. In other words, the solid state imagingdevice 73 according to the embodiment has a configuration where theparallel wiring lines 59 and 60 are omitted in the solid state imagingdevice 41 according to the first embodiment of FIG. 1.

In addition, for example, the parallel wiring line 57 is connected tothe selection gate electrode 51 of the selection transistor Tr4 to beused as a selection wiring line for supplying a selection pulse φSEL.The parallel wiring line 58 is connected to the reset gate electrode 55of the reset transistor Tr2 to be used as a reset wiring line forsupplying a reset pulse φRST. In addition, as seen from the top plane,wiring lines, for example, vertical signal lines 64 are formed to extendin the vertical direction by different metal layers so as to traversethe transfer wiring lines 35 to 38. In this case, the vertical signallines 64 are formed so as to intersect all the transfer wiring lines 35to 38 with the same line width.

The other configurations are the same as those of the first embodimentwhich is described with reference to FIG. 1. Therefore, the samecomponents corresponding to those of FIG. 1 are denoted by the samereference numerals, and the redundant description thereof is omitted.

In the solid state imaging device 73 according to the third embodiment,since the parallel wiring lines 57 and 58 which supply pulse voltagesare disposed to the outer sides of the outermost transfer wiring lines35 and 38, the potential changes of all the transfer wiring lines 35 to38 in the pixel driving period are equalized by the same capacitancecoupling. Therefore, the potential change of the transfer gate electrodeis suppressed, and the potential change in the silicon under thetransfer gate is suppressed, so that it is possible to suppress thevariation in the saturation signal amount between the pixels. Inaddition, although, for example, the vertical signal lines 64 aredisposed in the vertical direction, the vertical signal lines 64 areconfigured to intersect all the transfer wiring lines 35 to 38 with thesame line width, the influences of the potentials to the vertical signallines are uniformed over all the transfer wiring lines, so that anyproblem does not occur.

5. Fourth Embodiment Example of Configuration of Solid State ImagingDevice

FIG. 5 illustrates a solid state imaging device according to a fourthembodiment of the invention. The embodiment may be adapted to a backillumination type CMOS solid state imaging device, where pixel sharingunits of four pixels, eight pixels, or horizontal 2×vertical 2n (n is apositive integer, that is, n=1, 2, 3, . . . ) pixels are aligned in atwo-dimensional array shape. As the pixel sharing unit, horizontal2×vertical 2 (total four) pixels constitute one unit irrespective of thenumber of shared pixels. Therefore, similarly to FIG. 4, in FIG. 5, theembodiment is described by using one unit of the horizontal 2×vertical 2(total four) pixels.

As the solid state imaging device 75 according to the fourth embodiment,a back illumination type CMOS solid state imaging device where 8-pixelsharing units 42 are disposed in a two-dimensional array shape isadapted. The solid state imaging device 75 according to the fourthembodiment is configured by further inserting shield wiring lines 63between the wiring lines of the transfer wiring lines 35 to 38 andbetween the outermost transfer wiring lines 35 and 38 and the parallelwiring lines 57 and 58 adjacent thereto in the solid state imagingdevice 73 according to the third embodiment of FIG. 4. The shield wiringline 63 is preferably fixed to a power source voltage or a groundvoltage. However, the shield wiring line 63 may be floated in terms of apotential. The shield wiring line 63 is preferably constructed with ametal layer in the same layer as the transfer wiring lines 35 to 38. Inaddition, the shield wiring line 63 may be constructed with a metallayer upwardly or downwardly adjacent to the metal layer which becomes atransfer wiring line. The shield wiring line 63 is a wiring line foravoiding direct capacitance coupling between the transfer wiring lines35 to 38 or between the outermost transfer wiring lines 35 and 38 andthe parallel wiring lines adjacent thereto, for example, the parallelwiring lines 59 and 60.

The other configurations are the same as those of the third embodiment.Therefore, the same components corresponding to those of FIG. 4 aredenoted by the same reference numerals, and the redundant descriptionthereof is omitted.

In the solid state imaging device 75 according to the fourth embodiment,the shield wiring lines 63 are inserted between the wiring lines of thetransfer wiring lines 35 to 38 and between the outermost transfer wiringlines 35 and 38 and the parallel wiring lines 57 and 58 adjacentthereto, so that direct capacitance coupling between the transfer wiringlines is avoided. Accordingly, the potential changes of all the transferwiring lines 35 to 38 in the pixel driving period is suppressed, so thatit is possible to suppress the variation in the saturation signal amountbetween the pixels.

The solid state imaging device 75 is combined with the effect describedwith reference to FIG. 4, which is obtained by the layout of the pulsewiring lines according to the parallel wiring lines 57 and 58 adjacentto the outermost transfer wiring lines 35 and 38, so that a variation ina saturation signal amount is further suppressed. Therefore, althoughthe miniaturization of the pixel size is proceeding, it is possible tosuppress the potential change in the silicon under the transfer gate, sothat it is possible to suppress the variation in the saturation signalamount between the pixels. For this reason, the specification of thesaturation signal amount may be set to be high, so that it is possibleto improve pixel characteristics.

6. Fifth Embodiment Example of Configuration of Solid State ImagingDevice

FIG. 6 illustrates a solid state imaging device according to a fifthembodiment of the invention. As the solid state imaging device 77according to the fifth embodiment, a back illumination type CMOS solidstate imaging device where 4-pixel sharing units using horizontal2×vertical 2 (total four) pixels as one unit are disposed in atwo-dimensional array shape is adapted. In the solid state imagingdevice 77 according to the fifth embodiment, a pixel portion isconfigured by disposing 4-pixel sharing units 78, where photodiodes PD[PD1 to PD4] of the four pixels are disposed, in a two-dimensional arrayshape.

In the example, the 4-pixel sharing unit 78 is the area surrounded by adashed line A. The 4-pixel sharing unit 78 includes horizontal2×vertical 2 (total four) photodiodes PD. The two photodiodes PD1 andPD2 horizontally disposed are commonly connected to the first floatingdiffusion portion FDa, and the two photodiodes PD3 and PD4 horizontallydisposed are commonly connected to the second floating diffusion portionFDb.

On the other hand, a common transfer gate electrode is formed tostraddle the vertically-adjacent two photodiodes between the 4-pixelsharing units 78 which are adjacent to each other in the verticaldirection. In other words, a common first transfer gate electrode 81 isformed to straddle two photodiodes, that is, the photodiode PD1 in the4-pixel sharing unit 78 and the photodiode PD3 in the upper adjacent4-pixel sharing unit 78. A common second transfer gate electrode 82 isformed to straddle two photodiodes, that is, the photodiode PD2 in the4-pixel sharing unit 78 and the photodiode PD4 in the upper adjacent4-pixel sharing unit 78. A common third transfer gate electrode 83 isformed to straddle two photodiodes, that is, the photodiode PD3 in the4-pixel sharing unit 78 and the photodiode PD1 in the lower adjacent4-pixel sharing unit 78. A common fourth transfer gate electrode 81 isformed to straddle two photodiodes, that is, the photodiode PD4 in the4-pixel sharing unit 78 and photodiode PD2 in the lower adjacent 4-pixelsharing unit 78. Accordingly, four transfer transistors Tr11 to Tr14 areconfigured to be connected to the four photodiodes PD1 to PD4.

In the 4-pixel sharing unit 78 according to this example, although notshown, a reset transistor Tr2, an amplification transistor Tr3, and aselection transistor Tr4 are shared by four photodiodes PD. Variouslayouts for the reset transistor Tr2, the amplification transistor Tr3,and the selection transistor Tr4 may be considered.

In the embodiment, as seen from the top plane, in the 4-pixel sharingunit 78, two transfer wiring lines 79 and 80 are disposed to extend inthe horizontal direction and to be parallel to each other in thevertical direction. One transfer wiring line 79 is connected to, forexample, the first transfer gate electrode 81, and the other transferwiring line 80 is connected to, for example, the fourth transfer gateelectrode 82. The transfer wiring line 80 in the upper adjacent 4-pixelsharing unit 78 is connected to the second transfer gate electrode 82.The transfer wiring line 79 in the lower adjacent 4-pixel sharing unit78 is connected to the third transfer gate electrode 83.

Since the transfer gate electrode is formed over the two pixels, thenumber of the transfer wiring lines may be decreased. In this case,since two transfer wiring lines 79 and 80 are disposed to be in parallelto each other, at least one of the transfer wiring lines is disposed inthe horizontal direction to pass over the photodiodes PD, preferably, totraverse the substantially central portions of the photodiodes PD. Inthis example, the two transfer wiring lines 79 and 80 are disposed topass over the photodiodes PD.

The shield wiring lines 86 are disposed in parallel to each otherbetween the two transfer wiring lines 79 and 80 between the 4-pixelsharing units 78 which are adjacent to each other in the verticaldirection. In addition, a parallel wiring line 85 is disposed to be inparallel to the transfer wiring lines 79 and 80 between the photodiodesPD which are adjacent to each other in the vertical direction in the4-pixel sharing unit 78.

The shield wiring line 86 may be used as a wiring line which supplies aconstant voltage by using a power source voltage or a ground voltage. Inaddition, since the two transfer wiring lines 79 and 80 constitutes oneset, the shield wiring line 86 may be used as a pulse wiring line whichsupplies a pulse voltage. In this case, the adjacent parallel wiringline 85 other than the shield wiring line 86 are used between pulsewiring lines or between wiring lines which supply constant voltages.

The parallel wiring line 85 may be used as a wiring line which suppliesa fixed voltage or a pulse wiring line which supplies a pulse voltage.The fixed voltage is a power source voltage or a ground voltage.Available combinations of voltages which are supplied to the shieldwiring line 86 and the parallel wiring line 85 are as follows. One ofthe shield wiring line 86 and the parallel wiring line 85 may be used asa pulse wiring line, and the other may be used for a constant voltage.Both of the shield wiring line 86 and the parallel wiring line 85 may beused for pulse voltages. Both of the shield wiring line 86 and theparallel wiring line 85 are used for constant voltages. Herein,similarly to the aforementioned examples, the pulse wiring lines arereset wiring lines and selection wiring lines which supply the necessarypluses to the reset transistors and selection transistors.

The upper and lower parallel wiring lines 85 may have to be wiring lineswhich supply the same type of voltage (a pulse voltage or a fixedvoltage). Referring to the transfer wiring lines 79, the parallel wiringlines 85 have a relatively large influence on the transfer wiring lines79 in terms of capacitance. The same description may be made withrespect to the upper and lower parallel wiring lines 85 and the upperand lower transfer wiring lines 79. If one of the upper and lowerparallel wiring lines 85 is in a pulse voltage and the other is in aconstant voltage, the parallel wiring line 85 seen from the transferwiring line 79 becomes a different wiring line as seen periodically. Inorder to avoid this problem, the upper and lower parallel wiring lines85 may have to be the wiring lines which supply the same type of voltage(a pulse voltage or a constant voltage).

In the solid state imaging device 77 according to the fifth embodiment,the charges of the pixels are read out in the following manner. Thephotodiodes PD1 to PD4 are sequentially read, and firstly a pulsevoltage is input to the transfer wiring line 79 in the shared unit, sothat the charges are transferred from the photodiode PD1 to the floatingdiffusion portion FD. At this time, the photodiode PD3 in the upper-sideshared unit 78 is simultaneously read. The selection transistors of theupper-side and lower-side shared units including the shared unit 78 areturned on at shifted timings, so that the photodiode PD1 and thephotodiode PD3 of the upper-side shared unit are sequentially read.Next, in order to read the photodiode PD2, the transfer wiring line 80in the upper-side shared unit is turned on, so that the charges of thephotodiode PD2 are transferred to the floating diffusion portion FD. Atthis time, the charges of the photodiode PD4 in the upper-side sharedunit are also simultaneously transferred, and similarly to thephotodiode PD1, the selection transistor is turned on at a shiftedtiming, so the photodiode PD2 and the photodiode PD4 in the upper-sideshared unit are read. With respect to the photodiodes PD3 and PD4 in theshared unit 78, the reading is performed in a similar manner.

In the solid state imaging device 77 according to the fifth embodiment,since the shield wiring line 86 of a constant voltage is insertedbetween the transfer wiring lines 79 and 80 between the 4-pixel sharingunits 78 which are adjacent to each other in the vertical direction, itis possible to reduce the coupling capacitance between the transferwiring lines. Accordingly, the potential change in all the transferwiring lines in the pixel driving period is suppressed, and the changeof the potential in the silicon is suppressed, so that it is possible tosuppress the variation in the saturation signal amount between thepixels.

Even in the case where the shield wiring line 86 is used as a pulsewiring line, it is possible to suppress the change of the capacitancecoupling between the adjacent wiring lines of the transfer wiring lines79 and 80, so that it is possible to suppress the variation in thesaturation signal amount between the pixels. In addition, even in thecase where the shield wiring line 86 is configured not to be inserted,the interval between the transfer wiring lines 79 and 80 is allowed tobe increased, and the transfer wiring lines 79 and 80 are disposed topass over the photodiodes PD, so that a constant voltage or a pulsevoltage may be supplied to the parallel wiring line 85. Accordingly, theinfluence of the capacitance coupling is reduced, so that it is possibleto suppress the variation in the saturation signal amount between thepixels.

7. Sixth Embodiment Example of Configuration of Solid State ImagingDevice

FIG. 7 illustrates a solid state imaging device according to a sixthembodiment of the invention. In the embodiment, a back illumination typeCMOS solid state imaging device where 4-pixel sharing units where fourpixels are disposed in the vertical direction or 2-pixel sharing unitswhere two pixels are disposed in the vertical direction are disposed ina two-dimensional array shape is adapted. With respect to such a pixelsharing unit, since two-pixel sharing is periodically disposed, thepixel sharing unit is described by using one unit of horizontal1×vertical 2 (total two) pixels.

In FIG. 7, a dashed line 87 indicates a 4-pixel sharing unit havinghorizontal 1×vertical 4 (total four) pixels, and a dashed line 88indicates a 2-pixel sharing unit having horizontal 1×vertical 2 (totaltwo) pixels. In the sixth embodiment, a solid state imaging device 89 isconfigured by disposing the 4-pixel sharing units 87 in atwo-dimensional array shape, and a solid state imaging device 90 isconfigured by disposing the 2-pixel sharing units 88 in atwo-dimensional array shape.

In the 2-pixel sharing solid state imaging device 89 according to thesixth embodiment, the 2-pixel sharing unit 88 includes two photodiodesPD [PD1 and PD2] constituting two pixels in the vertical direction andone shared floating diffusion portion FD. In addition, the solid stateimaging device 89 also includes first and second transfer transistorsTr11 and Tr12 having transfer gate electrodes 91 and 92 and, althoughnot shown, a reset transistor Tr2, an amplification transistor Tr3, anda selection transistor Tr4.

In the solid state imaging device 89, the transfer wiring lines 95 and96 which are connected to the transfer gate electrodes 91 and 92 aredisposed to extend in the horizontal direction and to be in parallel toeach other in the vertical direction. The transfer wiring lines 95 and96 are disposed so that at least one of the transfer wiring lines 95 and96 passes over the photodiodes PD, preferably, traverses thesubstantially central portions of the photodiodes PD. In this example,two transfer wiring lines 95 and 96 are disposed so as to traverse thesubstantially central portions of the photodiodes PD1 and PD2.

In the embodiment, particularly, as seen from the top plane, the shieldwiring line 97 which extends in the horizontal direction is disposedbetween the two transfer wiring lines 95 and 96, and the parallel wiringlines 98 and 99 which are in parallel to the transfer wiring lines 95and 96 are disposed in the outer sides of the two transfer wiring lines95 and 96. The shield wiring line 97 may be used as a wiring line whichsupplies a constant voltage by using a power source voltage or a groundvoltage. The shield wiring line 97 and the parallel wiring lines 98 and99 may be constructed with a metal layer in the same layer as thetransfer wiring lines 95 and 96. Alternatively, the shield wiring line97 and the parallel wiring lines 98 and 99 may also be constructed witha metal layer as an upper or lower layer of a metal layer of thetransfer wiring lines 95 and 96.

Alternatively, the shield wiring line 97 may be configured as a pulsewiring line which supplies a pulse voltage. In this case, the adjacentwiring lines other than the shield wiring line 97, that is, the parallelwiring lines 98 and 99 are used between pulse wiring lines or betweenwiring lines which supply constant voltages.

In addition, the shield wiring line 97 may not be inserted, the intervalbetween the transfer wiring lines 95 and 96 may be increased, and thetwo transfer wiring lines 95 and 96 may pass over the photodiodes PD, sothat the parallel wiring lines 98 and 99 may be configured as pulsewiring lines or wiring lines which supply constant voltages.

In the 2-pixel sharing solid state imaging device 90 according to thesixth embodiment, the shield wiring line 97 of a constant voltage isinserted between the two transfer wiring lines 95 and 96, so that it ispossible to avoid direct capacitance coupling between the transferwiring lines 95 and 96. Accordingly, the change in the electrodes of allthe transfer wiring lines 93 and 94 in the pixel driving period issuppressed, and the change of the potential in the silicon issuppressed, so that it is possible to suppress the variation in thesaturation signal amount between the pixels.

Even in the case where the shield wiring line 97 is used as a pulsewiring line, it is possible to suppress the change of the capacitancecoupling between the adjacent wiring lines of the transfer wiring lines95 and 96, so that it is possible to suppress the variation in thesaturation signal amount between the pixels. In addition, even in thecase where the shield wiring line 97 is configured not to be inserted,the interval between the transfer wiring lines 95 and 96 is allowed tobe increased, and the transfer wiring lines 95 and 96 are disposed topass over the photodiodes PD, so that a constant voltage or a pulsevoltage may be supplied to the parallel wiring lines 98 and 99.Accordingly, the influence of the capacitance coupling is reduced, sothat it is possible to suppress the variation in the saturation signalamount between the pixels.

The 4-pixel sharing solid state imaging device 89 according to the sixthembodiment includes four photodiodes PD [PD1 to PD4] constituting fourpixels in the vertical direction and two shared floating diffusionportions FD within the 4-pixel sharing unit 87. In addition, the 4-pixelsharing solid state imaging device 89 also include first to fourthtransfer transistors Tr11 to Tr14 having transfer gate electrodes 91,92, 93, and 94, and, although not shown, a reset transistor Tr2, anamplification transistor Tr3, and selection transistor Tr4.

In the embodiment, although not illustrated, similarly, the transferwiring lines 95 and 96, the shield wiring line 97, and the parallelwiring line 99 are disposed to the upper-side two pixels.

In the 4-pixel sharing solid state imaging device 89 according to thesixth embodiment, by the same effects as the aforementioned solid stateimaging device 90, it is possible to suppress a variation in asaturation signal amount between pixels.

In the solid state imaging device according to the above examples,electrons are used as the signal charges. However, a solid state imagingdevice using holes as the signal charges may be adapted. In this case,the conduction type of each semiconductor area is configured as being aninverted conduction type.

In the aforementioned examples, the invention is adapted to apixel-shared CMOS solid state imaging device. However, the invention maybe adapted to other CMOS solid state imaging devices where unit pixelsare disposed in a two-dimensional array shape.

In the aforementioned examples, the invention is adapted to a backillumination type CMOS solid state imaging device. However, theinvention may also be adapted to a front illumination type CMOS solidstate imaging device.

The invention may be adapted to a CMOS solid state imaging device havingcolor filters in a Bayer array or a CMOS solid state imaging devicehaving color filters in a honeycomb array where pixels are arrayedslantedly. Even in these cases, transfer wiring lines, parallel wiringlines, and shield wiring lines are disposed to extend in the horizontaldirection.

8. Seventh Embodiment Example of Configuration of Electronic Apparatus

The aforementioned solid state imaging device according to theembodiment of the invention may be adapted to an electronic apparatus,for example, a camera system such as a digital camera or a video camera,a mobile phone having a photographing function, other apparatuses havinga photographing function, or the like.

FIG. 12 illustrates a camera as an example of the electronic apparatusaccording to a seventh embodiment of the embodiment of the invention. Inan example of the camera according to the embodiment, a video cameracapable of photographing a still picture or a moving picture is used. Acamera 111 according to the embodiment includes a solid state imagingdevice 112, an optical system 113 which guides incident light to a lightsensing sensor portion of the solid state imaging device 112, and ashutter unit 114. In addition, the camera 111 also includes a drivingcircuit 115 which drives the solid state imaging device 112 and a signalprocessing circuit 116 which processes an output signal of the solidstate imaging device 112.

As the solid state imaging device 112, any one of the CMOS solid stateimaging device according to the aforementioned embodiments may be used.It is preferable that, as the solid state imaging device 112,particularly, a pixel-sharing back illumination type CMOS solid stateimaging device is used. The optical system (optical lens) 113 allowsimage light (incident light) from a subject to be formed on an imagingplane of the solid state imaging device 112. Accordingly, signal chargesare accumulated in the solid state imaging device 112 for apredetermined time interval. The optical system 113 may be configured asan optical lens system including a plurality of optical lenses. Theshutter unit 114 controls a light illuminating period and a lightshielding period for the solid state imaging device 112. The drivingcircuit 115 supplies driving signals for controlling a transferoperation of the solid state imaging device 112 and a shutter operationof the shutter unit 114. The signal transferring of the solid stateimaging device 112 is performed based on the driving signal (timingsignal) supplied from the driving circuit 115. The signal processingcircuit 116 processes various types of signals. The processed imagesignal is stored in a storage medium such as a memory or output to amonitor.

According to an electronic apparatus such as a camera according to theseventh embodiment, in the solid state imaging device 112, it ispossible to suppress a variation of a saturation signal amount involvedwith miniaturization of a pixel size. Therefore, it is possible toprovide a high-quality electronic apparatus of which the image qualityis improved.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2009-272441 filedin the Japan Patent Office on Nov. 30, 2009, the entire contents ofwhich are hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A solid state imaging device comprising: a pixel portion where pixelsharing units are disposed in an array shape and where another one pixeltransistor group excluding transfer transistors is shared by a pluralityof photoelectric conversion portions; transfer wiring lines which areconnected to the transfer gate electrodes of the transfer transistors ofthe pixel sharing unit and which are disposed to extend in a horizontaldirection and to be in parallel in a vertical direction as seen from thetop plane; and parallel wiring lines which are disposed to be adjacentto the necessary transfer wiring lines in the pixel sharing unit andwhich are disposed to be in parallel to the transfer wiring lines asseen from the top plane, wherein voltages which are used to suppresspotential change of the transfer gate electrodes are supplied to theparallel wiring lines.
 2. The solid state imaging device according toclaim 1, wherein the pixel sharing unit is configured so that 2×2npixels (n is a positive integer) are shared, wherein the parallel wiringlines are disposed to be adjacent to the outermost transfer wiring linesamong the plurality of the transfer wiring lines in the pixel sharingunit, and wherein a pulse voltage is supplied to at least one of theparallel wiring lines.
 3. The solid state imaging device according toclaim 1, wherein the transfer wiring lines of the transfer transistorsare constructed with a metal layer in the same layer or in metal layersof the upper and lower adjacent layers, and wherein the parallel wiringlines are constructed with a metal layer in the same layer as thetransfer wiring lines or with a metal layer in one of the upper andlower adjacent layers of the transfer wiring lines.
 4. The solid stateimaging device according claim 1, further comprising shield wiring lineswhich are disposed between the transfer wiring lines and between thetransfer wiring lines and the parallel wiring lines and which aredisposed to extend in the horizontal direction as seen from the topplane, wherein the potential of the shield wiring line is a constantpotential or a floating potential.
 5. The solid state imaging deviceaccording to claim 1, further comprising two parallel wiring lines whichare constructed with a metal layer in another layer at outer sides ofthe outermost transfer wiring lines, wherein a pulse voltage is suppliedto one of the two parallel wiring lines, and a constant voltage issupplied to the other.
 6. The solid state imaging device according toclaim 2, further comprising: parallel wiring lines which are disposed tobe adjacent to the outermost transfer wiring lines and which areconstructed with a metal layer in the same layer as the transfer wiringlines and are supplied with a pulse voltage; and other wiring lineswhich are constructed with a metal layer in the layer different from thetransfer wiring lines and the parallel wiring lines and which aredisposed in the vertical direction so as to traverse the transfer wiringlines and the parallel wiring lines.
 7. The solid state imaging deviceaccording to claim 6, further comprising shield wiring lines which aredisposed between the transfer wiring lines and between the transferwiring lines and the parallel wiring lines as seen from the top planeand which are disposed to extend in the horizontal direction, whereinthe potential of the shield wiring lines are a fixed potential or afloating potential.
 8. The solid state imaging device according to claim1, wherein the pixel sharing unit is configured so that 2×2 pixels areshared, where the transfer gate electrodes of two pixels which areadjacent to each other in the vertical direction are formed as a commonelectrode, wherein a shield wiring line is formed between the transferwiring lines of the two pixels which are adjacent to each other in thevertical direction, and wherein a constant voltage or a pulse voltage issupplied to the shield wiring lines.
 9. The solid state imaging deviceaccording to claim 1, wherein the pixel sharing unit is configured sothat four pixels or two pixels which are disposed in the verticaldirection are shared, wherein shield wiring lines are disposed betweenthe transfer wiring lines, and wherein a constant voltage or a pulsevoltage is supplied to the shield wiring lines.
 10. The solid stateimaging device according to claim 1, wherein at least one transferwiring line is disposed to pass over the photoelectric conversionportion.
 11. The solid state imaging device according to claim 1,wherein at least one transfer wiring line is disposed to pass over thephotoelectric conversion portion which is disposed in the horizontaldirection as seen from the top plane, and wherein a wiring line layerhaving a plurality of layers is formed at the side opposite to a lightincident plane, so that a back illumination type is configured.
 12. Thesolid state imaging device according to claim 1, wherein a wiring linelayer having a plurality of layers is formed at the side of a lightincident plane, so that a front illumination type is configured.
 13. Asolid state imaging device comprising: a pixel portion where unit pixelsconfigured with a photoelectric conversion portion and a pixeltransistor are disposed in an array shape; transfer wiring lines whichare connected to the transfer gate electrodes of transfer transistorsincluded in the pixel transistors of unit pixels and which are disposedto extend in a horizontal direction and to be in parallel in a verticaldirection as seen from the top plane; and parallel wiring lines whichare disposed to be adjacent to the outermost transfer wiring lines andwhich are disposed to be in parallel to the transfer wiring lines asseen from the top plane, wherein a pulse voltage is supplied to at leastone of the parallel wiring lines.
 14. The solid state imaging deviceaccording to claim 13, further comprising shield wiring lines which aredisposed between the transfer wiring lines and between the transferwiring lines and the parallel wiring lines as seen from the top planeand which are disposed to extend in the horizontal direction, whereinthe potential of the shield wiring lines are a constant potential or afloating potential.
 15. An electronic apparatus comprising: a solidstate imaging device; an optical system which guides incident light tophotodiodes of the solid state imaging device; and a signal processingcircuit which processes an output signal of the solid state imagingdevice, wherein the solid state imaging device is configured as thesolid state imaging device according to claim 1.